1. Field of the Invention
This invention relates to a pressure sensor, more particularly to a pressure sensor having a high sensitivity and able to accurately detect a pressure of a high pressure fluid.
2. Description of the Related Art
A known pressure sensor used for the above purpose comprises a cylindrical detecting housing having an internal space therein, a cylindrical sensing body provided inside the internal space of the housing and having a cavity therein, one end of which is closed, a diaphragm provided at the closed end of the cavity, and a strain gauge made of a semiconductor or the like mounted on one surface of the closed end of the cavity opposite to the surface thereof which is subjected to a pressure.
The pressure sensor mentioned above is used to measure a pressure by allowing a pressurized medium to be introduced into the cavity portion from an open end of the sensing body and impinged on the diaphragm, whereby the pressure on the sensing body is detected by using the strain gauge to measure the amount of the strain imposed on the diaphragm.
In this kind of pressure sensor, the contacting portion formed between the sensing body and the housing is usually fixed by welding, and therefore problems such as a reduction of the sealing ability of the welded portion due to corrosion, a breakage of the welded portion caused by the high pressure imposed on the entire sensing body, especially when measuring a high pressure fluid, and a displacement of the sensing body, or in the worst case, a detachment thereof from the housing, arise, and therefore, this type of pressure sensor is not reliable when used for detecting a pressure of a high pressure liquid, due to an uncertain sealing ability which renders the sensor unsafe.